Mis sold phone

I bought a Blackberry mobile phone in January on Vodafone network, but the phone was unlocked. I asked the salesman if I would be able to simply put my Virgin SIM into the phone and everything, including Blackberry messenger, would work and he said it would. It didn't work, and as I found out later that day by searching the internet it was because I have a 30day rolling contract with Virgin, and so the Blackberry data service wouldn't work.

Having discovered this I went to a Virgin shop and they said that the blackberry data service should be up and running within the first quarter of the year, but yesterday when I went in, they said it was unlikely to ever work.

Having been sold this phone, and wrongly told it would work with my SIM, where do I stand regarding getting a refund for this phone?

I have had a look on this site and have found threads with similar issues, but different items. What legislation or guidelines can I use to back me up if the store refuse to refund, if this is indeed my statutory right?

Thanks for all replies, in advance...